Sunn 2000S ground problem

[bigrig]

Untraceable ground noise in the head somewhere. I've removed the chassis and all looks well. Yet I'm suspect that the power cord has been replaced at some point since 1972. I was shocked to fine no ground wire in the cord nor any apparent point to ground from the power cord or in the chassis.

Does anyone know the proper method of grounding this monster?

[txstrat]

I'd add a three prong cord and if theres no ground connector I'd add one to one of the PT bolts. The earth wire goes to this point.

[bigrig]

Thank you so much for your suggestion. Pardon my ignorance but I want to be certain. PT bolts?

[txstrat]

One of the bolts the power transformer (PT) is fixed with.

[bigrig]

Got it. Thanks again!